The overall objective of this research program is to develop a gene cloning (recombinant DNA) system in the oral streptococci. Using such methodologies we anticipate being able to approach the study of the genetics and biochemistry of bacterial oral colonization and cario genicity. Our grant-supported work has led to the discovery of a limited number of phenotypically cryptic plasmids in Streptococcus mutans and Streptococcus ferus (formerly S. mutans ssp. ferus). Primary goals in this regard were to identify clinically important plasmids in the oral streptococci and to adapt these plasmids for use as molecular cloning vehicles in the oral streptococci. An extension of the development of this system has been the study of R (resistance) plasmid uptake and incorporation into S. sanguis by genetic transformation. Both of these lines of endeavor are expected to bring us to the threshold of a feasible host-vector molecular cloning system in the oral streptococci. Such a recombinant DNA system shall enable the genetic dissection of the genome of oral streptococci. This approach should greatly expand our understanding of bacterial colonization and virulence in the human oral cavity and hopefully provide insight into means aimed at controlling dental plaque development.